When news broke recently that the crash of Malaysia Air Flight 17 was almost certainly caused by a Russian missile, it brought to mind that other MH accident—the still-unsolved disappearance of MH370 on its flight to Beijing two-and-a-half years ago. Yet the two disasters are strikingly different: Just days after MH17 was shot from the sky over Ukraine in July 2014 on a flight from Amsterdam to Kuala Lumpur, killing all 298 aboard, the wreckage and black boxes had been found. The main unanswered question was who fired the missile. But in the case of MH370, a costly and thus far fruitless underwater search for the 777—presumed to be at the bottom of the Indian Ocean—is about to wrap up, conspiracy theories continue to flourish, ranging from the predictable “pilot did it” scenarios to allegations that Russia, too, had a hand in this one.

But now, a book from aviation reporter and investigator Christine Negroni makes a compelling case for a possible explanation that hasn’t gotten much attention: hypoxia, or a lack of oxygen caused by depressurization inside the aircraft cabin, incapacitated the pilots and ultimately everyone on board, even as the plane flew on for hours on autopilot until it ran out of fuel and presumably crashed into the sea.

Negroni’s book, The Crash Detectives, out this week from Penguin Publishers, doesn’t focus only on MH370, but it puts it into context by chronicling a string of what the subtitle describes as the “world’s most mysterious air disasters”—including some long-ago cases like Amelia Earhart’s last flight, and the strange crash of a plane that killed UN secretary-general Dag Hammarskjöld. And it plumbs the reasons why some accidents are particularly hard to crack.

But what exactly is hypoxia, and how could it lead otherwise capable pilots to crash a plane?

The simple answer is that planes flying above 10,000 feet must be pressurized to a livable altitude of around 8,000 feet above sea level, otherwise, people aboard would suffer from dangerous low levels of oxygen and, the higher the plane, the more rapid the loss of consciousness. Instances of depressurization are rare, and can be caused by a sudden event, such as an explosion, or, more commonly at lower altitudes, failure to activate the pressurization controls. In either case an alarm should sound, and pilots are trained to don oxygen masks or descend to below 10,000 feet. But pilots have only seconds to act, Negroni tells Condé Nast Traveler, and the initial symptoms of hypoxia are like intoxication—giving people a false sense of confidence, and impairing judgment.

“It’s really two failures,” Negroni says. “It’s the failure that caused the hypoxia and failure to use the mask.” Using several other cases involving hypoxia as a guide—including the crash of Helios Flight 522 out of Athens in 2005, Negroni lays out a strong argument for how hypoxia would explain many of the unanswered questions about MH370, such as the lack of distress call, the disabling of the transponder that signals the plane’s location, and the seemingly inexplicable movements of the plane as it changed course before vanishing from screens completely. And as for what caused the cabin to lose pressure in the first place, she examines several theories, including whether the lithium battery shipment in the cargo hold could have caught fire. A more likely cause, she argues, is an electrical failure that knocked out the plane’s systems, and points to clues from previous incidents involving leaks into the critical electronics bay on other large Boeing and Airbus aircraft. Others, including The Daily Beast's Clive Irving and David Soucie, an aviation safety analyst for CNN, have also backed the hypoxia theory.

And while Negroni is not optimistic the plane and its black boxes will be retrieved from the bottom of the ocean, she says it’s illusory to think that the wreckage alone would solve the mystery.

“I say ‘Stop using the (missing) black boxes as a dodge,’” says Negroni. After all, if the plane was flying for hours in a kind of zombie state before it plunged into the sea, those recorders might not yield much valuable data anyway, as they record only the last hours of the flight. Just as a murder case can be solved without a body, using evidence such as maintenance records, previous episodes involving that particular aircraft model, and any other sources, can help investigators piece together a likely scenario that at the very least can help prevent other similar accidents from occurring in the future.